The present invention relates to a charging circuit for a rechargeable battery and, particularly, to a battery charging circuit capable of measuring voltage of a battery such as nickel-cadmium battery regardless of temperature condition in a place where the battery is located.
The rechargeable battery such as nickel-cadmium battery has been widely used with recent popularization of portable personal computer and telephone, etc., and thus a charging circuit capable of exactly charging such a battery to a predetermined voltage level has been also popularized.
A conventional charging circuit includes a measuring circuit for equivalently measuring a charged voltage level of the battery by converting a battery voltage into a signal having a periodical waveform. The circuit for converting voltage into periodic waveform has, however, a problem that it can not measure an exact charge voltage in a location where temperature is changed largely within a short time, for reasons to be described later.